Although research and development on technology for making hydrogen a major energy source have been going on for some time, the conventional methods of storing and carrying hydrogen were accompanied by safety risks such as explosions. Recently, hydrogen-absorbing organic compounds have been studied as hydrogen storage materials, for their ability to stably and reversibly store hydrogen by forming chemical bonds. However, these compounds require vessels or sealed tanks maintained at high pressure and/or temperature and often encounter difficulty in relasing the hydrogen gas. A safer and more efficient system for storing and carrying hydrogen has been needed.

The research group discovered a ketone (fluorenone) polymer, which can be molded as a plastic sheet, and can fix hydrogen via a simple electrolytic hydrogenation at -1.5V (versus Ag/AgCl) in water at room temperature. Furthermore, the fluorenol polymer can release hydrogen when heated to 80 degrees Celsius with an aqueous iridium catalyst. The group proved that under mild conditions the cycle of fixing and releasing hydrogen can be repeated without significant deterioration, pointing the way to the developement of a plastic container for hydrogen that can be carried in your pocket.

The advantages of the ketone/alcohol polymer include easy handling, moldability, robustness, non-flammability and low toxicity, and the research results are also expected to contribute to building distributed energy systems in remote areas.

The research results were published in the British science magazine Nature Communications on September 30.